Systems used to localize the origin of cardiac arrhythmias measure potentials (e.g. in millivolts) in the cardiac chambers and localize them on a three dimensional representation of the cardiac chamber wall. The measurement of the electrical activity present on the cardiac walls is called mapping. For this purpose, a multiple electrode mapping catheter may be positioned within the heart such that multiple potentials can be simultaneously measured at different locations on the wall of the cardiac chamber without having direct wall contact (non-contact mapping). The cardiac chamber is visualized as a three dimensional structure, either directly by moving one or more mapping electrodes within the corresponding heart chamber or by importing an anatomical geometry of the cardiac chamber from an imaging device (e.g. Computed Tomography, MRI, or ultrasound). The electrical activity within the heart can be measured with the multi-electrode mapping catheter, which may be able to simultaneously measure potentials at different points in three dimensional space. In the current systems, the measured potentials from the non-contact multi-electrode mapping catheter do not directly correspond to the electrical activity on the cardiac wall as measured with an electrode with direct wall contact (contact mapping). The measured potentials of the non-contact mapping system have to be converted with computer programs and extrapolated into virtual electrograms projected on the heart chamber of the mapping system.
U.S. Pat. No. 5,297,549 (Beatty, et al.) discloses a method of generating a three-dimensional map of electrical activity in a heart chamber as well as a two-dimensional map of the electrical activity within the endocardial surface. Beatty generates the information via an array of electrodes placed in a heart chamber utilizing impedance plethysmography, while one electrode serves as a reference.
The current conversion methods suffer various instabilities, and further processing, termed regularization, must be applied to maintain stability. Regularization decreases spatial resolution. Another limitation of the current methods is that the provided potentials represent only the mean electrical activity summed across a large region of tissue, with cells consisting of membranes separating electrical dipoles.
Since the localization of cardiac arrhythmias by the use of potentials is imprecise, the successful treatment of cardiac arrhythmias has been difficult and has demonstrated limited success and reliability. There is, therefore, a need for improved methods of localizing cardiac arrhythmias.